Familial combined hyperlipidaemia: use of stable isotopes to demonstrate overproduction of very low-density lipoprotein apolipoprotein B by the liver.

We have assessed very low-density lipoprotein apolipoprotein B production, using [15N]glycine as an endogenous marker in a 9-hour primed constant infusion protocol, in four adult male subjects with familial combined hyperlipidaemia and in four normolipidaemic adult male controls. The mean very low-density lipoprotein apolipoprotein B absolute synthetic rate was significantly greater in the familial combined hyperlipidaemic subjects than in control subjects (26.31 +/- 8.37 vs 9.36 +/- 4.07 mg/kg per 24 h, p less than 0.05). These results confirm findings using exogenous radioisotope labelling techniques that very low-density lipoprotein apolipoprotein B production is significantly increased in most patients with familial combined hyperlipidaemia. A modified 9-hour protocol can be safely done repeatedly and in children and pregnant women.